/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: IteratorPool.java,v 1.2.4.1 2005/09/14 19:45:19 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.axes;

import java.util.ArrayList;

import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xml.internal.utils.WrappedRuntimeException;

/**
 * Pool of object of a given type to pick from to help memory usage
 * @xsl.usage internal
 */
public final class IteratorPool implements java.io.Serializable {
    static final long serialVersionUID = -460927331149566998L;

    /**
     * Type of objects in this pool.
     */
    private final DTMIterator m_orig;

    /**
     * Stack of given objects this points to.
     */
    private final ArrayList m_freeStack;

    /**
     * Constructor IteratorPool
     *
     * @param original The original iterator from which all others will be cloned.
     */
    public IteratorPool(DTMIterator original) {
        m_orig = original;
        m_freeStack = new ArrayList();
    }

    /**
     * Get an instance of the given object in this pool
     *
     * @return An instance of the given object
     */
    public synchronized DTMIterator getInstanceOrThrow() throws CloneNotSupportedException {
        // Check if the pool is empty.
        if (m_freeStack.isEmpty()) {

            // Create a new object if so.
            return (DTMIterator) m_orig.clone();
        } else {
            // Remove object from end of free pool.
            DTMIterator result = (DTMIterator) m_freeStack.remove(m_freeStack.size() - 1);
            return result;
        }
    }

    /**
     * Get an instance of the given object in this pool
     *
     * @return An instance of the given object
     */
    public synchronized DTMIterator getInstance() {
        // Check if the pool is empty.
        if (m_freeStack.isEmpty()) {

            // Create a new object if so.
            try {
                return (DTMIterator) m_orig.clone();
            } catch (Exception ex) {
                throw new WrappedRuntimeException(ex);
            }
        } else {
            // Remove object from end of free pool.
            DTMIterator result = (DTMIterator) m_freeStack.remove(m_freeStack.size() - 1);
            return result;
        }
    }

    /**
     * Add an instance of the given object to the pool
     *
     *
     * @param obj Object to add.
     */
    public synchronized void freeInstance(DTMIterator obj) {
        m_freeStack.add(obj);
    }
}
